Motors are an electromagnetic device for electric energy conversion according to the law of electromagnetic induction, which mainly include direct current motors and alternating current motors. The direct current motors or universal brush motors require a brush assembly. The brush assembly includes a brush and a brush cage. The brush is mounted in the brush cage and is biased by a spring. The brush contacts a commutator to transfer the electrical current from the brush to the commutator.
FIG. 1 illustrates a conventional brush assembly. The brush assembly includes a brush 2, a brush cage 1, and a spring (not shown). The brush 2 is received in the brush cage 1 and biased by the spring. Two stop plates 12 extend outwardly from one end of the brush cage 1. Each stop plate 12 includes a hook 13 at a distal end thereof. The stop plates 12 are configured to stop two coil portions 3 of the spring. When the brush 2 moves toward a commutator under the influence of the force of the spring, i.e. the brush 2 extends out of an end 11 of the brush cage 1, the hooks 13 catch the two coil portions 3 of the spring, making the spring coil up. The two stop plates 12 are at the same angle to an outer surface of the brush cage 1.
However, in the conventional brush assembly, in order to ensure that the brush 2 smoothly extents and retracts in the brush cage 1, the brush 2 and the brush cage 1 usually have a large gap there between, i.e. a side surface 21 of the brush 2 and an inner surface of the brush cage 1 have a large gap there between. As a result, during operation of the motor, vibration of the brush 2 can easily occur which may cause abnormal noises.